A small adenomatous polyp (tubular adenoma) is seen here. This lesion is called a "tubular adenoma" because of the rounded nature of the neoplastic glands that form it. It has smooth surfaces and is discrete. Such lesions are common in adults. Small ones are virtually always benign. Those larger than 2 cm carry a much greater risk for development of a carcinoma, having randomly collected mutations in genes such as APC, SMAD-4, K-RAS, and p53 over the years. The colonoscopic appearance of rectal polyps that proved to be tubular adenomas are seen below. [Note the diverticula in the background of the left panel.]